ABSTRACT Marshallese are a subpopulation of Pacific Islanders that are experiencing significant health disparities, with some of the highest documented rates of type 2 diabetes mellitus (T2DM) in the world.1-6 Estimates of T2DM in the Marshallese range from 20% to 50%, compared to 8.3% for the US population.1-6 Pilot data (n = 401) documented that Marshallese immigrants in Arkansas have extremely high rates of T2DM (38.4%), and pre- diabetes (32.6%), and only 10% engage in self-management behaviors. The Marshallese immigrant population has increased rapidly in United States (US). Marshallese immigrants experience unique barriers to self- management of T2DM, as well as unique cultural assets that can be leveraged to help mitigate these barriers. The research team worked with the Marshallese community to develop a culturally-adapted family model of DSMES (Family-DSMES). The intervention uses an asset-based approach predicated upon Marshallese?s collectivist culture and leverages the influence of family to help Marshallese immigrants engage in self- management behaviors. The initial implementation and evaluation of Family-DSMES was taught to one family at a time in patients? homes. While the Family-DSMES was successful at improving patient outcomes, there are challenges and expenses for delivery in a home setting to one family at a time that make the intervention unsustainable. The proposed study will test the intervention in faith-based organizations (FBOs) (as opposed to patients? homes) with groups of families (as opposed to one family at a time). With these significant changes, we hypothesize that the Family-DSME will be effective and sustainable. Our specific aims are: 1) Test the effectiveness of Family-DSMES to improve diabetes-related outcomes among Marshallese patients; 2) Evaluate the effect of Family-DSMES on family members; and 3) Conduct a cost-effectiveness analysis to understand intervention costs in relationship to outcomes. We will conduct a fully-powered cluster RCT that includes 288 Marshallese patients with T2DM and 288 of their family members. A wait-list control arm that includes patients and family members will serve as an untreated comparison group during the study. The RCT will be conducted at 24 Marshallese FBOs, and it will be taught by Marshallese community health workers. Data will be collected from patients and their family members in both arms of the study at baseline, immediately post-intervention, six months, and 12 months post-intervention. We will also obtain a medical records release to abstract participants? biometric outcomes at 18 and 24 months post-intervention. In addition to our primary analyses, we will examine the potential mediation effect perceived social (family) support has on patients? outcomes. We will also evaluate potential heterogeneity of treatment effects according to sex, nativity, and level of acculturation. While the Marshallese are a small population, this immigrant community is underrepresented in research, and they are experiencing a health crisis that must be addressed. Testing group delivery in FBOs is imperative to expanding the reach and long-term sustainability of the Family-DSMES.